Much has been made of Angelina Jolie's directing debut – it's not often that an A-list gossip-magazine stalwart sticks their neck out artistically – and this sombre, powerful, and undeniably gripping film is the result. As a high-profile Hollywood liberal and a UNHCR goodwill ambassador, her choice of material – the mass rapes committed by Bosnian Serb forces during the 1992-5 Bosnian war – will perhaps lay her open to the charge of furrowed-brow earnestness, but Jolie's considered, muscular approach means that she is treading a fine line between gruesome war-vérité and preachy grandstanding. To her credit, she nearly always gets it right, despite occasionally resorting to shorthand to get across complicated political or ideological positions.

In fact, In the Land of Blood and Honey is impressive in its lack of directorial flourishes: it feels like a film born out of scrupulous research and deeply felt conviction. Jolie's two protagonists are Bosniak Muslim painter Ajla (Zana Marjanović) and Bosnian Serb policeman Danijel (Goran Kostić): in the film's early pre-war scenes, which suggest Sarajevo as a paradise of an ethnic melting pot, they appear about to launch themselves into a heartfelt relationship, but a bomb blast in the dancehall where Ajla and Danijel meet puts a dramatic stop to it.

The detonation also signals the start of wider hostilities, and within a few months Ajla is taken prisoner by Bosnian Serb soldiers and moved with a group of women to a detention camp. It is here where the film's most disturbing scenes take place: the women are confined in what looks like a former school, and are subject to night-time visits from the soldiers who repeatedly drag them off to be to be sexually assaulted. Ajla herself manages to avoid this brutalisation as, as chance would have it, Danijel is the local commander of the Bosnian Serbs and, after peeling one soldier off her back, explains that they will leave her alone as they think she is now his "property".

Thereafter Danijel takes a protective interest in Ajla, installing her as his personal servant, bringing her with him when he is transferred, and then designating her as his "official artist" and keeping her sequestered in a barracks room.

Jolie's intention, clearly, is to present their relationship not only as a hideous distortion of what might have been, warped and corroded by the brutalities of the war, but also as metaphor for the conflict itself: riven by ancient prejudices, self-hate, and double standards, and the application of violence (sexual and otherwise) to sustain the male-Serb hegemony. This, rather weirdly, has the effect of making Danijel the more complex, dramatically interesting character: Ajla is a largely passive victim-figure, penned in a single room, and given only a narrow range of terror and relief, while most of the horrors go on elsewhere. Danijel, of course, is an active participant in them, indulging in an Oedipal conflict with his ultra-nationalist general father, all the while attempting to hide his tender feelings for his prisoner.

It's with Danijel that things get a little tricky, however. Jolie must structure the drama so as not to make him too hateful, and so he is shown only lukewarmly prosecuting his duties as a Muslim-killer and village-burner. Then again, he is apparently "loved" by his men (all of whom appear to be standard-issue evil Serbs), and appears a fearsome fighter. Jolie tries to compensate for this character hole by having Danijel turn nasty at key points, but it's not an altogether successful patch. And the enclosed, inward-looking focus of the central relationship means Jolie must give one of the big emotional-jolt scenes to Ajla's sister, who disappears from the film for long stretches.

However, Jolie's grasp of the material is confident enough to mean that her film never slows down, or loses its way. If her film is more persuasive in its recreation of casual theatre-of-war brutality than the cinematically somewhat undernourished Danijel-Ajla axis, then that's a reflection of the film's priorities. But it also shows this is not simply a vanity project; Jolie has kept herself well in the background. And her film benefits all the more for it.